Cardiac diseases, such as stenocardia, myocardial infarction and heart failure, and cerebrovascular diseases, such as cerebral infarction, cerebral hemorrhage and subarachnoid hemorrhage, are correlated closely with high blood pressure. These diseases are the second and third leading cause of death in Japan, respectively. According to the National Livelihood Survey published in 1998 by the Ministry of Health and Welfare, the number of outpatients with hypertension amounts to 64 per 1000 patients, and hypertension ranks first in the etiology surveyed in Japan. Among the therapeutic measures aimed at high-blood pressure are antihypertensives, such as diuretic drugs, sympatholytic drugs, vasodilating drugs and angiotensin converting enzyme inhibitors. These medicaments are applied primarily to severe hypertension patients. On the other hand, general therapeutic methods aimed at improving lifestyle habits, such as diet therapy, exercise therapy, control of drinking and smoking, are acknowledged to be of importance, in that these methods are widely applicable to many hypertension patients ranging from mild hypertension through severe hypertension. Among them, dietary habit is said to be particularly important. And there are traditionally many kinds of food products said to have antihypertensive effects. Searches for antihypertensive materials derived from food have been conducted actively heretofore, and a number of active substances having such effects have been isolated and identified.
Chlorogenic acids, which are contained about 6 to 9% in a raw coffee bean, have an excellent antihypertensive effect (Patent Documents 1 and 2). Nonetheless, because caffeine is also contained normally 1 to 4% in a raw coffee bean, it is said that the excessive intake of such ingredients could cause adverse effects at the same time, such as hypersensitivity, nausea and sleeplessness. On this account, a method capable of selectively removing caffeine from a chlorogenic acid composition containing caffeine has been investigated.
So far, there have been some reports associated with decaffeinating methods, for example, a method of contacting coffee with a caffeine adsorbent such as activated carbon under 120 to 250 atm (Patent Document 3) and a method of contacting an aqueous solution containing caffeine with activated clay or acid clay to thereby selectively remove caffeine (Patent Document 4).
However, the former method relates to a supercritical extraction technology, and its process requires a great deal of facilities, so that this method lacks simplicity in terms of industrial operation. Furthermore, there is another problem in that this method brings a detrimental change to the composition of chlorogenic acids serving as active ingredients, without contributing to the selective removal of only caffeine. On the other hand, the latter method can selectively remove caffeine simply by use of activated clay or acid clay, but this method raised the problem that the recovery ratio of chlorogenic acids does not suffice.
In addition, a method characterized by performing extraction from raw coffee beans with an aqueous solvent, adsorbing chlorogenic acids with a synthesized adsorbent, and treating it with a dilute alkali to selectively obtain chlorogenic acids (Patent Document 5), and a method characterized by performing a treatment in contact with a strong-acid cation exchange resin to selectively obtain chlorogenic acids (Patent Document 6) can be mentioned. Nonetheless, these methods require cumbersome ion exchange treatments.
[Patent document 1]: JP-A-2002-53464
[Patent document 2]: JP-A-2002-87977
[Patent document 3]: JP-A-53-18772
[Patent document 4]: JP-A-06-142405
[Patent document 5]: JP-A-04-145049
[Patent document 6]: JP-A-04-145048